Astronomers discover one of the most ancient stars that formed in another galaxy

In a groundbreaking discovery, scientists have found a star from the second generation that originally formed in a different galaxy from our Milky Way.

Anirudh Chiti, a University of Chicago postdoctoral fellow and first author on a paper announcing the findings, and his colleagues look for stars that formed from the ashes of that first generation.

The second generation of stars is exceedingly rare and ancient, with estimates suggesting that perhaps fewer than one in 100,000 stars in the Milky Way belongs to this second generation.

"You really are fishing needles out of haystacks," Chiti said.

For this study, the team focused on the stars that make up the Large Magellanic Cloud (LMC) - a satellite galaxy of the Milky Way, visible as a bright swath of stars in the Southern Hemisphere.

Researchers believe that LMC was once a separate galaxy and it fell into our Milky Way galaxy just a few billion years ago. This makes it particularly interesting because its oldest stars were formed outside the Milky Way, providing a unique opportunity to study the conditions of the early universe beyond our galaxy.

Using the European Space Agency's Gaia satellite and the Magellan Telescope in Chile, the team catalogued ten ancient stars within the LMC. One of these stars immediately jumped out as an oddity due to its significantly lower concentration of heavier elements compared to others observed in the LMC, suggesting it was formed from the remnants of the universe's first stars before heavier elements became more abundant through subsequent generations of stellar life and death.

The scientists found that this star had a lot less carbon than iron compared to what we see in Milky Way stars.

"That was very intriguing, and it suggests that perhaps carbon enhancement of the earliest generation, as we see in the Milky Way, was not universal," Chiti said.

Their findings also corroborated other studies that have suggested that the Large Magellanic Cloud made much fewer stars early on compared to the Milky Way.

Chiti is currently leading an imaging program that aims to map out a large portion of the southern sky to find the earliest stars possible.

Their findings are published in the journal Nature Astronomy.